The present invention relates generally to traffic responsive control systems for automatic sliding doors. More particularly, the present invention relates to a new and improved traffic responsive control system for sensing traffic at or in the vicinity of the doorway threshold and for maintaining the sliding doors in an opened position until the traffic clears the door threshold.
A number of sliding door systems are automatically operable for initiating an opening sequence upon sensing the motion or presence of traffic at the doorway, or receiving a command from a push plate, card reader, mat or other operation initiating means. A number of automatic door systems employ infrared sensors which sense the traffic approaching the doorway by sensing changes in received passive infrared radiation. The infrared sensors sense traffic for initiating the door opening sequence. Infrared transmitters have also been used for generating safety beams for insuring that the door does not inadvertantly open or close.
The use of infrared radiation for sensing traffic in connection with automatic door systems is subject to a number of design and operational constraints. For example, the moveable door which traverses through a portion of the traffic path presents a potential for interference with the detection system and must be taken into account in the system design or otherwise compensated for by the detection processing system. The transmitters and detectors must be positioned so as to cover a sufficiently wide area of the traffic path while also minimizing interference from the moving door. Accordingly, relatively complex transmitter and detector beam paths and/or specially designed photoemitter and photodedector lens configurations are incorporated into many infrared sensor systems. The safety beam infrared sensor applications frequently do not provide a large region of coverage. Many such systems also require the separate installation of several units.
Scoville et al U.S. Pat. No. 3,852,592 discloses an automatic swing-door operator which employs a traffic control having an infrared emitter and detector. The emitter is mounted at the header of the door system and generates a directed energy beam having a preselected divergence which spans the path of travel of traffic approaching the doorway. The emitter is located substantially on the hinge line of the door. The detector is mounted adjacent the opposite jamb and has an axis of sensitivity which is oriented transversely of the beam of energy.
Kornbrekke et al U.S. Pat. No. 4,565,029 discloses an automatic door installation which employs four traffic sensors mounted on the door jambs on opposite sides of the doorway opening. The sensors have infrared energy emitters and infrared energy receivers for sensing the doorway traffic. Two sensors are employed to cover the exit or swing side of the doorway. A threshold sensor is employed to cover the threshold area. An entrance sensor is employed to cover the entrance side of the doorway. The entrance and exit sensors each have a plurality of radiant energy emitters with angularly spaced beam axes which provide relatively broad coverage areas intersecting the travel path. The emitters are selectively deactivated as the door is swung to its opened and closed positions to avoid sensing the door. The emitters of each of the sensors are pulsed in a pre-determined sequence and the receivers are synchronously activated to receive reflected radiant energy from the emitters.
Jonsson U.S. Pat. No. 4,590,410 and Jonsson U.S. Pat. No. 4,560,912 each disclose an infrared object sensing apparatus for an automatic door wherein a plurality of radiation emitting elements are arranged to radiate a diverging beam of radiation into a selected region of space. A plurality of radiation sensing elements are arranged in proximity to the emitting elements for receiving radiation reflected from traffic within the region. The transmitting and receiving elements may be arranged in separate linear arrays which are separated by relatively small distances.